Ionic liquid 1-sulfonicacidpropyl-3-methylimidazole hydrosulfate [MIMPS][HSO₄] was prepared as a catalyst to synthesize 2, 6-diamino-3, 5-dinitropyrazine-1-oxide(LLM-105) from nitration of 2, 6-diacetamido-pyrazine-1-oxide with N₂O₅/solvents. The structures of intermediates and LLM-105 were determined by ¹H NMR, IR and MS. The effects of reaction solvents, amount of [MIMPS][HSO₄], reaction temperature, reaction time and repeated use of [MIMPS][HSO₄] on the yield of LLM-105 were studied. Results show that the optimized reaction conditions are: CH₃NO₂ as solvent; reaction temperature 55 ℃; reaction time 6 h. The yield of LLM-105 is 72.2%.The ionic liquid is suitable for repetition use.